A fabric for use as a covering fabric for down wear or futons is required to have low air permeability to suppress leakage of cotton or down, and, in addition, is also required to be lightweight and thin.
Such a fabric is conventionally made from natural fibers, such as silk or cotton, excellent in feeling and comfort. However, the fabric made of the natural fiber is low in tear strength and poor in durability; when the fabric is used particularly for down jacket, there is caused a problem that cotton or down spouts out easily from an elbow or sleeve portion thereof.
A polyester multifilament, a nylon multifilament and a conjugated synthetic fiber fabric thereof have also been used as the above-mentioned fabric. These fabrics are frequently used particularly for coats, blousons, golf wears, outdoor wears for sports, and so forth since they are soft, light, windproof, highly water-repellent, and highly fastness.
However, in order to allow the woven fabrics to have down-proofness to suppress leakage of down, the woven fabrics need to have a dense structure, which causes a problem that the woven fabrics become hard.
Further, in order to respond to the need for reducing the weight and thickness of a woven fabric without lowering tear strength, a woven fabric that can achieve a reduction in weight without lowering tear strength has been proposed. Such a woven fabric is made from yarns having a small fineness, and also uses high-strength yarns that are different from base yarns and have a specific fineness. For example, Patent Document 1 discloses a lightweight woven fabric that is constituted from base yarns having a fineness of 10 dtex to 30 dtex and reinforcing yarns having a fineness of 20 dtex to 60 dtex and has a cover factor of 1300 to 1700 and a tear strength of 8 N or more. However, the woven fabric disclosed in Patent Document 1 is made from polyamide fibers whose shrinkage ratio is higher than that of a polyester, and therefore has a problem that the weave structure thereof tends to deform during washing. This makes it impossible for the woven fabric to retain low air permeability after washing.
Patent Document 2 discloses a woven fabric for use as a covering fabric for futons. The woven fabric is constituted from synthetic multifilaments, each of which is made from modified cross-section single yarns having a degree of modification of 2 to 7 and has a fineness of 15 dtex to 35 dtex, and has a cover factor of 1500 to 2000, a tear strength of 6 to 15 N, and an air permeability before washing of 0.3 to 1.5 cc/cm2/s. However, in Patent Document 2, there is no description about the durability of the woven fabric against, for example, washing based on air permeability. Further, conventional products have a problem in that the air permeability thereof is reduced due to repeated wear, compression for storage, and washing during long-time use and therefore leakage of down is likely to occur.